This invention relates to an element for laminating ink jet prints, more particularly to a polymeric support having thereon a porous, fusible, transferable protection layer.
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink jet recording element typically comprises a support having on at least one surface thereof a base layer for absorbing fluid and an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
Ink jet prints prepared by printing onto ink jet recording elements are subject to environmental degradation such as water smearing and light fade. For example, since ink jet dyes are water-soluble, they can migrate from their location in the ink-receiving layer when water comes in contact with the recording element after imaging.
To reduce the vulnerability of prints to degradation and to enhance gloss, ink jet prints are often laminated. Typically, such conventional lamination is a process whereby a continuous polymeric film bearing an adhesive is brought into contact with the surface of the print. Heat and/or pressure is then used to affix the continuous polymeric film to the print surface. The continuous polymeric film then serves as a barrier layer that is impermeable to water and further acts to diminish the fading of the print image caused by light.
However, there is a problem with prior art laminating films since they are typically supplied in roll format and must be cut, or less desirably torn, to separate the laminated print from the continuous roll of laminating film. A requirement to cut adds expense to a laminator design that is required to run in a continuous mode.
U.S. Pat. No. 5,662,976 discloses an assembly for creating laminated cards which comprises a sheet of card stock with a release coating and a sheet of laminating film adhering to the release coating. A card form is cut into the sheet of card stock, and a lamination strip, which is sufficiently large to fold over so as to laminate both surfaces of the card, is cut into the lamination sheet. After printing, the card and the lamination strip are removed, and the lamination strip folded over to laminate the card. However, there is a problem with this laminating film in that expensive cutting and perforating steps are required to prepare the laminated card.
U.S. Pat. No. 5,387,573 discloses a dye-donor element for thermal dye transfer comprising a support and a transferable protection layer wherein the transferable protection layer is less than about 1xcexc thick and contains particles in an amount of up to about 75% of the transferable protection layer. However, there is no disclosure in this patent that the protection layer can be used with ink jet prints.
It is an object of the invention to provide a transfer laminating element for laminating ink jet prints wherein the protection layer is sufficiently thick to protect ink jet images from degradation by water, and yet can be employed without resort to expensive cutting steps. It is another object to provide a transfer laminating element for laminating an ink jet print of arbitrary geometric shape. It is still another object to provide a transfer laminating element that allows for the direct visual distinction between laminated and unlaminated regions of the print.
These and other objects are provided by the present invention which comprises a transfer laminating element for laminating ink jet prints comprising a flexible, polymeric support having thereon a porous, fusible, transferable protection layer comprising fusible, thermoplastic polymeric particles in a polymeric binder, the protection layer having a thickness of between about 2 and about 100 xcexcm and a particle-to-binder ratio of between about 95:5 and about 70:30, the thermoplastic polymeric particles having a particle size of less than about 10 xcexcm and a Tm or softening point of greater than about 50xc2x0 C. and the polymeric binder having a Tg of less than about 20xc2x0 C.
In using the invention, the transfer laminating element is contacted with an ink jet image using heat and pressure to form a fused composite. Within the composite, the porous, fusible, transferable protection layer fuses to become a substantially continuous film which is optically clear. After cooling below the Tg of the polymer used to make the particles, the support is peeled from the composite. The substantially continuous film easily separates, without cutting, from the unfused porous region, thereby forming a protection layer on the surface of the inkjet image.
As noted above, the particle-to-binder ratio in the protection layer is between about 95:5 and about 70:30. If the particle-to-binder ratio is above the range stated, the layer will not have any cohesive strength. If the particle-to-binder ratio is below the range stated, the layer will not be porous, and on peeling the support away from the cooled composite after laminating, a continuous film is present which must be cut.
It is believed that when a fusible, transferable protection layer is used which is porous, cutting is obviated by the weak cohesive strength at the interface between the area of the substantially continuous film formed on fusing and the unfused, porous area. Thus, the interface acts as a micro-perforated edge of the film that facilitates a clean rupture. Further, during the fusing step, otherwise entrained air escapes via the interface between the substantially continuous film and the unfused, porous area.
The polymer used to make the fusible, thermoplastic polymeric particles employed in the invention may be an amorphous polymer which has softening point greater than about 50xc2x0 C., such as an amorphous polyester, e.g., Kao C(copyright) (Kao Corp.) or an acrylic polymer such as Carboset 526(copyright) (BF Goodrich Specialy Chemicals); or a partially crystalline polymer having a Tm greater than about 50xc2x0 C., such as a partially crystalline polyester, e.g., Griltex Polyester(copyright) (EMS American Grilon Corp) or an ethylene-vinyl acetate copolymer such as Elvax(copyright) (DuPont Corp.); or a thermoplastic, modified cellulose such as Ethocel(copyright) (Dow Chemical Co.), etc. In a preferred embodiment, the fusible, thermoplastic polymeric particles are made from an amorphous polyester having a silica shell. In another preferred embodiment, the fusible, thermoplastic polymeric particles contain a UV-absorber.
The fusible, thermoplastic polymeric particles used in the invention may be made using various techniques, such as, for example, evaporative limited coalescence as described in U.S. Pat. No. 4,833,060, limited coalescence as described in U.S. Pat. No. 5,354,799, grinding as described in U.S. Pat. No. 4,304,360, or cryogenic grinding as described in U.S. Pat. No. 4,273,294.
As noted above, the polymer used to make the fusible, thermoplastic particles will have a Tm or softening point greater than about 50xc2x0 C., preferably between about 60xc2x0 C. and 150xc2x0 C. The Tm is measured using a differential scanning calorimeter (DSC). In a preferred embodiment, the Tm is between about 60xc2x0 C. and 120xc2x0 C. A softening point of a polymer can be measured by the Ring and Ball method as described in ASTM E28. In addition, the polymer used to make the fusible, thermoplastic particles usually will have a Tg of less than about 100xc2x0 C., preferably between about 0xc2x0 C. and 90xc2x0 C.
As noted above, the polymeric binder used in the invention has a Tg of less than about 20xc2x0 C., preferably between xe2x88x9260xc2x0 C. and 20xc2x0 C. The polymeric binder used in the invention may be, for example, a polyurethane such as a Witcobond(copyright) Aqueous Urethane Dispersion (Witco Corp.), a vinyl acetate-ethylene copolymer emulsion, an ethylene-vinyl chloride copolymer emulsion, a vinyl acetate-vinyl chloride-ethylene terpolymer emulsion such as Airflex(copyright) (Air Products Corp.), or an acrylic emulsion such as Flexbond(copyright) (Air Products Corp). In a preferred embodiment, the binder comprises a polyurethane.
A subbing/release layer may also be used to provide adhesion between the porous, fusible, transferable protection layer and the support. The subbing/release layer must be capable of initially adhering the protection layer to the support and must be capable of subsequently releasing the protection layer from the support upon application of heat and pressure followed by cooling. Any material that performs this adhesion/release function can be used. In general, a coated subbing/release layer has a final coating weight of about 90 mg/m2. Suitable materials include, for example, lattices such as a terpolymer latex of acrylonitrile, vinylidene chloride and acrylic acid, or partially hydrolyzed vinyl chloride-vinyl acetate copolymers. Alternatively, a subbing/release layer can be generated directly on the support surface by corona-discharge-treatment of the support prior to applying the porous, fusible, transferable protection layer.
As the flexible, polymeric support for the invention, there may be used, for example, various plastics including a polyester-type resin such as poly(ethylene terephthalate), poly(ethylene naphthalate), polycarbonate resins, polystyrene resins, polysulfone resins, methacrylic resins, cellophane, acetate plastics, cellulose diacetate, cellulose triacetate, vinyl chloride resins and polyester diacetate. The thickness of the support may be, for example, from about 12 to about 500 xcexcm, preferably from about 75 to about 300 xcexcm. In a preferred embodiment, the support is a transparent poly(ethylene terephthalate) film.
Since the transfer lamination element may come in contact with other image recording articles or the drive or transport mechanisms of laminating devices, additives such as surfactants, lubricants, matte particles and the like may be added to the element to the extent that they do not degrade the properties of interest.
The protection layer described above may be coated by conventional coating means onto the support such as wound wire rod coating, slot coating, slide hopper coating, gravure, curtain coating and the like.
Ink jet inks used to prepare the images to be laminated by the transfer lamination element of the invention are well-known in the art. The ink compositions used in ink jet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives, and the like. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. The dyes used in such compositions are typically water-soluble direct or acid type dyes. Such liquid compositions have been described extensively in the prior art including, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and 4,781,758, the disclosures of which are hereby incorporated by reference.
Although the elements disclosed herein have been referred to primarily as being useful for laminating ink jet prints, they also can be used to protect images created employing other technologies such as photographic prints, laser printer prints, prints made via offset lithography and the like.